The present invention relates to devices for transporting and/or guiding flexible commodities, especially flexible radiation-sensitive articles including X-ray films which are to be transported and/or guided in the dry region of a processing machine. More particularly, the invention relates to improvements in transporting and/or guiding devices of the type wherein a shaft is surrounded by a cylindrical member which consists of synthetic plastic material and confines an antistatic additive.
A machine which processes photosensitive and other radiation-sensitive material normally comprises one or more sections wherein sheets or webs of flexible radiation-sensitive material must be transported in dry condition. Examples of such machines are copying, enlarging and developing machines which include one or more sections wherein photographic paper or other photosensitive material must be transported in non-wetted condition prior to development of latent images. This applies for inlet regions of developing machines where the exposed but yet to be developed film or photographic paper advances on its way toward the first of a series of liquid-containing vessels, as well as for apparatus which introduce X-ray film into or remove X-ray film from cassettes or analogous containers. A similar situation arises in X-ray machines wherein relatively large or relatively small loose sheets of radiation-sensitive material must be withdrawn from their cassettes or magazines, transported to a position of register with a source of X-rays, and thereupon advanced from such source to the developing station.
If the article-contacting surfaces of the transporting and/or guiding devices (normally in the form of rollers) are the exposed surfaces or cylindrical or otherwise configurated members which consist of synthetic plastic material, the members are highly likely to become electrostatically charged so that a discharge of accumulated electrostatic potential takes place on contact with the web of photosensitive material. This results in an imaging of the discharge and attendant damage to or total loss of utility of the photosensitive material. Such discharge is especially undesirable when the material to be transported and/or guided already carries one or more latent images which are about to be developed, e.g., latent images which represent portions of a human body and are about to be developed for study by physicians and/or other qualified persons.
Attempts to prevent such discharges include the use of rollers whose article-contacting portions consist of high-quality steel and which are installed in the dry regions or sections of machines for developing, inserting, removing and/or otherwise processing webs, sheets or strips of radiation-sensitive material. A drawback of such conventional rollers is their high cost and pronounced weight; this drawback is particularly serious when the dry section of a machine requires a substantial number of rollers or analogous article-guiding and/or transporting devices.
Other prior proposals include the utilization of so-called antiflash rubber rollers. The cylindrical mantles of such rollers consist of rubber and the elastomeric material confines an antistatic component which is intended to reduce the extent of electrostatic charging. A drawback of such prior proposal is that rubber rollers are not suited for a variety of uses in machines for the processing of radiation-sensitive material. For example, the ability of rubber rollers to transport films along relatively short paths which exhibit a highly pronounced curvature is extremely limited. Moreover, the useful life of rubber rollers is relatively short and their ability to withstand corrosive influences in many types of film processing machines is either insufficient or negligible.
U.S. Pat. No. 3,611,028 granted Oct. 5, 1971 to Whitmore discloses a roller whose cylindrical article-contacting portion consists of elastomeric synthetic plastic material embodying an antistatic agent. The patentee proposes to employ a vinyl chloride resin which is mixed with alkyl phthalyl alkyl glycolate. Tests with such rollers indicate that the extent of electrostatic charging is reduced so that the rollers can be used for the transport and/or guidance of certain types of photosensitive material. However, their resistance to acceptance of an electrostatic charge does not suffice to warrent or justify their use in connection with the transport and/or guidance of X-ray film or the like.